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Coefficient
of thermal expansion may be either linear
or volumetric. The coefficient of linear thermal
expansion is the change in length per unit of
length for a 1° rise in temperature. The
coefficient of volumetric thermal expansion is
the change in volume divided by the product of
the original volume and the change in temperature.
In solids, the coefficient of volumetric expansion
is three times the coefficient of linear expansion.
Because elastomeric
compounds have much higher coefficients of
expansion than steel or aluminum (i.e. than the
materials from which many glands are
made), thermal
expansion may cause an already tight seal
to swell and
overfill the gland as temperatures rise. Glands
have even been known to rupture under the force
exerted by an expanding seal. Conversely, a seal
design that provides only minimal squeeze in
a low temperature setting cannot look to thermal
effects for help in tightening the seal.
THERMAL
PROPERTIES MAIN PAGE
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“Because
O-rings often face extreme heat or extreme cold, there are important thermal properties
you must consider.”
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